Silvio Cherubini for ASFIN2 20 November 2012
NUCLEAR ASTROPHYSICS AT LABORATORI
NAZIONALI DEL SUD
ITALY – JAPAN 2012
Milano, 20-23 November 2012
NUCLEAR ASTROPHYSICS
@
CATANIA
LABORATORI NAZIONALI DEL SUD
Silvio Cherubini CNS-The University of Tokyo RIKEN Campus, Wako Dec 17th , 2009
→ Nuclear Astrophysics and Indirect Methods
→ Recent applications of THM
18F+p and
11B(p, a )
→ VERY Recent application of VNM
→ Non-THM applications (Big Bang,
16N b- delayed alpha decay)
Summary
History of Nuclear Astrophysics in short!
- Eddington, Aston, Gamow, Bethe: “energy production in stars” (1920-1939) - Gamow introduced the Gamow factor (1928), convoluted with the Maxwell distribution this fixes the typical energy for nuclear reactions in stars
Reaction rate: r = N1 N2 v (v)
(# reactions volume-1 time-1) exp(-2ph)
exp(-E/kT)
- B2FH: kind of formal definition of nucleosyntesis in stars (1957)
GAMOW WINDOW 10-100 keV (non esplosiva)
Nano- Picobarn (even less!)
Miserable S/N ratio
Estrapolation
Dedicated Experiments / Lab (LUNA)
Electron Screening
Estrapolation…
Indirect Methods (CD, ANC,
THM
)THM: a primer
=Trojan Horse nucleus
EBA > EC
EC
S x x x
B
S A
Nuclear field
EC = Coulomb barrier between A and B EBA = relative energy between A and B
EBx= ECD – Q2 EBx = interaction energy B-x
Electron screening
removed by construction
C D
x
Idea: get the 2-body cross-section of the process
B + x → C + D
At astrophysical energies from the QUASI-FREE contribution of a 3-body reaction (C. Spitaleri, Folgaria 1990)
B + A → C + D + S
S
A = x S
18
F+p
15O+ a
18
F+d
15O+ a +n
d = n p
P C P
d3σ
3-body Reaction Virtual Decay Virtual reaction
(astrophysical process) A
B
S C D
x
=
Ax
S
x
B D
C
Assuming that a Quasi-free mechanism is dominant one can use the PWIA:
EBx= ECD-Q2b dΩC dΩD dEcm
KF·|Φ (Ps)|
2
dΩ dσN
Measured at high energy
Calculated e.g.
Montecarlo d3σ
3-body Reaction Virtual Decay Virtual reaction
(astrophysical process) A
B
S C D
x
=
Ax
S
x
B D
C
EBx= ECD-Q2b dΩC dΩD dEcm
KF·|Φ (P
s)|
2 dΩ dσNIndirectly Measured
/
Assuming that a Quasi-free mechanism is dominant one can
use the PWIA:
APPLICATION OF THE METHOD and tricky points
From the theoretical/phenmenological point of view
1. Selection of the three body reaction and of the Trojan Horse Nucleus depending on its cluster structure properties. This
affects the number and type of reaction mechanisms competing with the QF one and the cross section value of the QF channel itself (more in two slides)
2. Check of the presence/dominance of the QF mechanism (impulse distribution reconstruction, study of the angular distribution, Treiman-Yang criterion)
3. Reliability of the “ingredients” used in d2 derivation, e.g. of impulse distribution of the THl nucleus.
4. If one is measuring a cross section below the Coulomb barrier,
then has to correct the THM x-sec for penetration factor before comparing the THM results with the direct ones.
From the experimental point of view:
1) Optimization of the energy and angular resolution of the
experiment to obtain the necessary resolution in the ExB variable (relative energy of x-B (related to the cm energy of the
astrophysical process)
2) Background noise suppression (this is not THM specific...) including the PHYSICAL background (see next slide)
3) Avaailability of direct measurements (above the region where Electron Screening effects start to show up and if possible also above the Coulomb barrier).
D E
xB= f( D E
CD E
DDq
CDq
D)
PHYSICAL BACKGROUND: an example
6
Li+p →
3He+
afrom
6Li+d →
3He+
a n
Art of the TH: finding the phase space region where this diagram is dominant!
ADVANTAGES of the Method
1) The cross sections in the experiment are typical QF processes ones (mbarn/sr) though one is measuring a nuclear reaction at astrophysical energies
2) The THM x-section is purely NUCLEAR: no suppression effect due to Coulomb barrier
3) No electron screening effect: one can get INDEPENDENT pieces of information on the electron screening potential by comparison with direct data
4) The experimental setup is tipically simple enough
5) The THM can be extended to use QFR in studying NEUTRON induced reaction (VNM Virtual Neutron Method)
18
F+p
15O + a AT CRIB VIA THM
18
F+d
15O + a + n
Thick target method (also at CRIB) Indirect methods
Transfer reaction
For the star energetics this are peanuts!
18
F(p,
a)
15O
STATE OF THE ART
DIRECT EXPERIMENTTRIUMF DATA
C. E. Beer et al. PHYSICAL REVIEW C 83, 042801(R) (2011)
18/03/2013 16
THM Experiment kinematics… needs all!
nSpectator
A
B
S c d x
2H
18F 4He
15O
p E(18F) = 50 MeV
17
CRIB setup
1. Two beam production tests performed ( Nov . 2005, June 2006) 2. 3*10^5 pps obtained, 10^6 pps within the capabilities of the machine 3. Beam purity > 98%
4. Normalization and deffinitionof the beam particle by particle (PPACs)
BEAM PRODUCTION AT CRIB
18
EXPERIMENTAL SETUP
(other then CRIB...)
PPAC MCP
CD2 2
TARGET
DPSSD array
Front view of DPSSD array
DSSSD 0.5 m 9cm
24cm
Safety disk
ASTRHO:
Array of Silicons for TRojan HOrse
PPAC MCP CD2
particle by particle beam reconstruction
Experimental setup 3
How ASTRHO looks like in reality
(before PPAC explosion...)
The Italian-French-Japanese connection
21
Q-VALUE SPECTRUM
DETECTOR PAIRS:
8-1;7-1 CUTS:
“BEAM”+”THRES.”
+”MULT” +”CORR. TIME”
18F+d15N+a+p @ q=4.194 VNM+RIB!!!
18F+d15O+a+n @ q=0.658
18F+d18O+p+p @ q=0.213
18F+d18F+p+n @ q=-2.225
22
EVENT SELECTION
Red : 18F + d 15N + a + p Black: 18F + d 15O + a + n Blue: 18F + d 18F + p + n Green: 18F + d 18O + p + p “1”+“2”+“3”
23
Q-VALUE SPECTRUM
GOOD AGREEMENT with
Q-value expected position (0.658 MeV)
And energy beam profile (exp. Sigma 0.8 MeV)
Previous cuts + Erel-Erel correlation +E-Theta correlation
24
HINTS FOR QF MECHANISM
d s
N/d W
BARE NUCLEUS CROSS SECTION
FIRST TROJAN HORSE MEASUREMENT WITH RIBs !!!
38 keV
11
B(p,a
0)
8Be via
11B(d,a
0 8Be)n
L. Lamia et al.
among «al.»:
S. Kubono,
Y. Wakabayashi,
H. Yamaguchi
HULTEN FRESCO
S(E) by THM
S(E) by THM vs
Direct measurement
electron screening extraction
U
eTHM=472+-160 eV
U
edir=430+-80 eV
11/20/2012
V N M:
17O(n, a )
14C via
17O + d a +
14C +p
n
17
O + d
-40<ps<40 (MeV/c)
-40<ps<40 (MeV/c) 6
Li + d
Magnifying glass effect
VIRTUAL neutron source
A parasitic experiment
performed @ LNS, Catania E(17O) = 41 MeV
A dedicated
experiment at ND
Gulino et al. accepted for publication on PRC Rapid
Communication today!!!
angular distributions
Univ. Catania and INFN-LNS:
C. Spitaleri, S. C., L. Guardo, M. Gulino, S. Hayakawa, I. Indelicato, M. La Cognata, L. Lamia,R.G. Pizzone, S. Puglia, G.G. Rapisarda, S.
Romano, M.L. Sergi, R. Spartà, A. Tumino CNS, The University of Tokyo:
S. Kubono, H. Yamaguchi, Y. Wakabayashi, D.N. Binh,
RIKEN, Tohoku-, Tsukuba-, Yamagata-, Kyushu- University:
N. Iwasa, S. Kato, H. Komatsubara, S. Nishimura, T. Teranishi CSNSM, IN2P3/CNRS and Université Paris Sud:
A. Coc, N. de Séréville, F. Hammache Texas A&M University
R. Tribble, A. Mukhamedzanov, L. Trache RUB: Claus Rolfs
...I apologize with those I surely forgot!
33
Direct Measurements and inhomogeneous Big Bang
1H(n,)2H(n,)3H(d,n)4He(t,)7Li(n,)8
Li( a ,n)
11B
(n,)12B(b)12CLINCHPINS OF BIG BANG:
expansion, Cosmic Microwave Background, primordial nucleosynthesis…
BIG BANG SCENARIOS (depending on the phase transition from QGP to Hadronic Universe):
●
HOMOGENOUS Big-Bang
●
synthesis of elements stops at lithium
●
INHOMOGENEOUS Big-Bang
●
much wider set of primordial elements (up to carbon)
●
via the reaction chain:
+ scintillation beam monitor
EVERYTHING OK ?
Not really welcome guests…..
1) Leaky 7Li beam (no matter what you do, it is there!)
● 2) Neutrons from cyclotron and
● 3) Neutrons primary-beam induced
(really nasty ones)
Can we overcome these problems ?????
The experimental technique
The principle: we can suppress via
“software” what was not suppressed by the
“hardware” (S. Cherubini)
How?
The Recipe:
1 Apply a tagging procedure to the incoming 8Li ions using the MCP pair,
2 use this information to “switch on” the neutron detector only when a 8Li has been detected.
This allow for a dramatic reduction of the background neutrons, owing to their de-correlation with the MCP trigger signal Beam time needs (from known X-sec.)
50 ion/sec
6 days
BIG BANG result for 8
Li( a ,n)
11B
x-sec500 mbarn +- 170 mbar +- 70 mbarn Stat. Syst.
EPJ A-20, S. Cherubini et al.
+ series of papers
Direct measurements & Inhomogeneous BigBang
6 8
New runs of BIGBANG were the first experiment at
EXCYT
BUT the X-sec puzzle remined there...
Inclusive measurements → high Exclusive measurement → low ...
La Cognata et al., The Astrophysical Journal, 706:L251–L255, 2009 December 1
We proposed the following solution to the puzzle
... contribution from E1 levels at 2418 and -45 keV
--- destructive interference constructive interference
... contribution from E2 level
at -245 keV and direct capture --- destructive interference
constructive interference
C. E. Rolfs & W.S. Rodney Cauldrons in the cosmos
Study of the beta-delayed alpha decay of
16N
“A measurement of the β-delayed α decay of 16N is considered to be the best method presently available to provide a constrain for the E1 component, SE1 (300), of the 12 C(α,γ ) reaction”
X. D. Tang et al., Phys Rev C 81, 045809 (2010)
A view to the level diagram
~10-5
b-
levels contributing to E1 component in 12C(a,g)16O
x-sec
NEED TO MEASURE ALPHA DECAY SPECTRUM OF 16N DOWN TO ENERGIES WHERE THE INTERFERENCE BETWEEN 2418 AND -45 keV
LEVELS (in a-12C rel. energies) APPEARS (>1MeV)
“In a study of the 16N b-delayed decay, three aspects are important:
(1)a particles with energies down to 0.6 MeV have to be detected in coincidence with 12C ions of even lower energies ( 0.1 MeV). Any significant energy loss of the outgoing particles in the catcher foil will deform the shape of the spectrum.
(2) If a particle, emitted from the foil, is stopped in the support frame, only a part of the energy is deposited in the
gas. Such events must be clearly separated from the true coincidence events producing the interference peak.
(3) The detection efficiency must be constant over the energy range from 0.2 MeV to 2 MeV.”
X. D. Tang et al.
Phys Rev Lett 99 052502 (2007) 1), 2) No foil, no frame: NO PROBLEMS
3) Monitor the energy response of the detector event by event
Univ. Catania and INFN-LNS:
C. Spitaleri, S. C., L. Guardo, M. Gulino, S. Hayakawa, I. Indelicato, M. La Cognata, L. Lamia,R.G. Pizzone, S. Puglia, G.G. Rapisarda, S.
Romano, M.L. Sergi, R. Spartà, A. Tumino CNS, The University of Tokyo:
S. Kubono, H. Yamaguchi, Y. Wakabayashi, D.N. Binh,
RIKEN, Tohoku-, Tsukuba-, Yamagata-, Kyushu- University:
N. Iwasa, S. Kato, H. Komatsubara, S. Nishimura, T. Teranishi CSNSM, IN2P3/CNRS and Université Paris Sud:
A. Coc, N. de Séréville, F. Hammache Texas A&M University
R. Tribble, A. Mukhamedzanov, L. Trache RUB: Claus Rolfs
...I apologize with those I surely forgot!